O-Rings for Dm7

So after cleaning my Dm7 and taking out 2 brand new 2007 O-ring kit, i've come to noticed they are all either smushed like play-dol or hard and brittle. Where can i find the best quality o-rings at the best price for my Dm7. I know there is an O-ring dm7 layout out there. Thank you.

If you know the sizes you need, you can actually find them at pretty much any hardware store. The material is often referred to as Buna, or n-Buna and come in standard sizes. Know the sizes (from your manual) and you can make your own for what basically amounts to a nickel an o-ring, and you can make sure they aren't hard/brittle or smushed before you buy.